A form that is neither a symbol nor a cons is defined to be a self-evaluating object. Evaluating such an object yields the same object as a result.
Certain specific symbols and conses might also happen to be ``self-evaluating'' but only as a special case of a more general set of rules for the evaluation of symbols and conses; such objects are not considered to be self-evaluating objects.
The consequences are undefined if literal objects (including self-evaluating objects) are destructively modified.
18.104.22.168.3.1 Examples of Self-Evaluating Objects